Several devices that include a viewfinder of one form or another incorporate what is commonly referred to in the art as “eye-start” functionality. “Eye-start” refers to the attribute in which an action is initiated upon the detection of the user bringing the viewfinder of the device to his or her face. The term “eye-start” is a bit of a misnomer in that, in the typical case, the presence of the user's face, not his or her eye, is detected by the eye-start sensor. Although the eye-start functionality has various applications, eye-start is most often used in conjunction with film and digital still cameras to activate the autofocusing, autoexposure, and automatic white-balancing processes.
As is known in the art, autofocusing, in which the camera automatically focuses on an object within the camera's field of view, is a relatively time-consuming process in which the one or more lens elements of the camera are moved relative to the camera body until maximum contrast is detected for the object of interest. In most cameras, this process is begun when the user depresses the shutter-release button to a halfway position. Once the autofocusing process has been completed, the focus of the camera remains locked as long as the shutter-release button is maintained in the halfway-depressed position.
Although the halfway depression method works well for experienced users as a means for controlling the autofocusing process, it can fail for less savvy users who do not take the time to permit that process to be completed. For example, when a vacationer asks a stranger to take a picture of the vacationer and his family with his camera, such a stranger may just “poke” the shutter-release button in one swift motion. In such a case, an out-of-focus image may be captured or an incorrect image may be captured (e.g., when the camera is prematurely moved from the intended object).
These problems can be avoided when the eye-start functionality is used. In such a case, the autofocusing mechanism begins to operate as soon as the camera is brought up to the user's face. Therefore, the object of interest typically will be in focus by the time the user wishes to capture an image. The eye-start functionality also provides the added benefit of reducing the perceived time the user must wait for the camera to focus on the object. Specifically, once the camera has been brought up to the face and the user has composed the shot, the user may take the picture at will without having to depress the shutter-release button to a halfway position and hold it there until the autofocusing process is completed.
While eye-start can be an attractive feature in a camera or other device, conventional eye-start mechanisms can potentially make false determinations as to the proximity of the user's face. This is because most eye-start mechanisms comprise a light source and light sensor that are positioned external to the device viewfinder, for instance adjacent the viewfinder on a rear panel of the device housing. Therefore, if a camera with eye-start functionality is set down on a table next to another object, the camera can be “fooled” into believing the viewfinder has been brought up to the user's eye, and therefore may initiate the autofocusing process or other designated action. Such unintended operation is undesirable especially when it wastes power thereby shortening battery life.